1. Field of the Invention
The present invention relates to a sheet processing apparatus that performs a certain process on a sheet recording medium (referred to as “sheet” in this specification) that has been conveyed and an image forming apparatus that includes this sheet processing apparatus inside its body, such as a copier, a printer, a facsimile machine, or a digital MFP.
2. Description of the Related Art
So-called sheet processing apparatuses or sheet post-processing apparatuses, which are each arranged subsequently to an image forming apparatus and which perform at least one of aligning, sorting, stapling, and folding with respect to sheets printed by the image forming apparatus, are in widespread use. Most of these apparatuses perform alignment upon sorting, stapling, and folding. The alignment can be carried out in a sheet conveying direction or in a direction orthogonal to the sheet conveying direction. In the alignment in the sheet conveying direction, a rear end of a sheet is usually abutted against a rear end reference fence to carry out the alignment of sheets on a rear-end basis.
Known examples of this type of technique include the inventions disclosed in Japanese Patent Application Laid-open No. 2003-241460, Japanese Patent Application Laid-open No. 2006-193283, and Japanese Patent No. 3441897. Japanese Patent Application Laid-open No. 2003-241460 describes an example of an internally-discharging-type image forming apparatus having: an operation panel and an image reading unit for reading image data of an original, which are both positioned at an upper part of the apparatus main body; and an image forming unit, which performs imaging on a transfer sheet according to the image data from the image reading unit and which is disposed below the operation panel and the image reading unit. The transfer sheet on which an image has been formed is discharged onto a discharge tray provided in an internal open section, which is between the image reading unit and the image forming unit and which has a conveying path and a discharging space that are inside the apparatus main body.
Japanese Patent Application Laid-open No. 2006-193283 describes a sheet processing apparatus that swings a stacking surface of a processing tray when a sheet is discharged and when the sheet is aligned, to solve a problem of the sheet barely being able to return by its own weight, causing improper alignment when a temporary stacking tray is approximately horizontal.
Japanese Patent No. 3441897 discloses a sheet post-processing apparatus including a bifurcating claw, which is disposed near a downstream end of a conveying roller for conveying and discharging a copy sheet to a staple tray and near the staple tray and which performs switching between a non-staple conveying path and a staple conveying path. The bifurcating claw, being switched towards the staple conveying path, guides the copy sheet discharged onto the staple tray along a lateral surface thereof. The bifurcating claw is usually positioned in a direction to open the non-staple conveying path. As a staple mode is selected and a copy sheet is conveyed from an image forming apparatus, the bifurcating claw is rotated towards the staple conveying path to open the staple conveying path, and when the copy sheet is discharged to the staple tray, the bifurcating claw returns towards the non-staple conveying path to close the staple conveying path. This is repeated copy sheet by copy sheet.
Japanese Patent Application Laid-open No. 2003-241460 discloses a so-called internal discharge type image forming apparatus, but not an internally installed sheet post-processing apparatus. Japanese Patent Application Laid-open No. 2006-193283 discloses a structure to resolve the improper alignment in the temporary accumulation tray, but the structure is not the type to perform the alignment by causing the sheet to abut on the rear-end basis. Japanese Patent No. 3441897 discloses the sheet post-processing apparatus that repeats the operation of switching the sheet conveying directions sheet by sheet, but does not make any reference to sheet guides used in the switching operation and the downsizing of that guiding structure.